Low power, again

[btoscano]

Hey all,



I've started experiencing another problem with low power. Last year it was determined that the guide pin in the IP was sticking. I had that fixed and the problem went away... until 2 weeks ago. At first it seemed related to "summer fuel" in "cold weather". I would stop off and add additives, and all better... until next morning so I'd top off and add additives again. But now that doesn't seem to matter. Sunday was just not a very good day for power and it just sounds worse at idle. Is it a new ULSD?



So far I've changed the fuel filter, checked the air filter, pulled the intake hose and verified the turbo still looks good, pulled the fan belt to make sure nothing is very tight, jacked up the rear wheels to make sure the brakes feel okay, and pulled the bed and checked the tank (clean, clean, clean). Some of those things were just too easy not to check so I did them just as sanity checks.



The real surprise is that I've noticed what I think is higher than normal boost levels by 3-4 psi. I don't recall the truck running 5 psi uphill in 3rd at 30 MPH. I also don't recall it requiring 5-6 psi to run downhill on the freeway at 72-75 (used to 3-4) and 10-12 uphill (used to 8-9). However, maximum boost also seems lower... So it almost seems like the timing has been retarded except that smoke has NOT increased and max boost has NOT increased (and maybe decresed 1-2 psi). Is this ULSD??? Winter fuel???



Any ideas?



Thanks,

Brian

 

[JLEONARD]

Winter fuel yields about 2 mpg less than summer fuel, so assuming 20 mpg that's about a 10 % loss assuming mpg and power are directly related... and I think that's a fair assumption.

So if your power loss is "about" 10% it could be winter fuel.

Make sense to anybody else?

I don't know what winter ULSD will take away from the table... .

 

[btoscano]

I just don't recall any previous winters with Cummins B5. 9's being this noticable. Are the refiners cutting the fuel with extra low BTU anti-gel agents? How does that explain the higher average boost and lower total boost? Does it mean I'm having the push the engine more to get around hence the higher boost and since the fuel has lower BTU's I'm also not going to get as much boost?



Brian

 

[JLEONARD]

Less BTU would mean lower heat and lower boost, so there is something else going on.

 

[Greenleaf]

What is a "Winter Fuel"? :-laf

 

[btoscano]

Winter fuel has additives or kerosene added to reduce the gel point.



Brian

 

[btoscano]

I removed the AFC cover and inspected it and everything looked fine. I did not see any problems with the banjo fitting. Is there something I could be missing there? I'll jack up the front end and check that the tires both spin freely.



I had the truck in the driveway and start and stopped it a dozen times. It seemed that a few times the truck started and sounded good, but then settled into a worse sounding noise. One time it even surged back and forth until I pumped the throttle on the pump. Even more interesting was the fan. It is not warm by any means outside and the fan would start running at full speed. There is also a little play in the clutch bearing. I wonder if the clutch is shot and running the fan at full speed. That may account for higher boost pressures and engine drag.



Brian

 

[btoscano]

The truck pulls 4 psi of boost at WOT standing still in my driveway. I think it may be the fan clutch!



Brian

 

[btoscano]

Okay, I removed the fan clutch and at WOT standing still in the driveway it still runs at 4 psi boost... and without any fan belt at all it runs at 3 psi boost. Is this normal? Or is the trans or something internal to the engine causing some drag? Or possibly the exhaust causing some problems? I don't know how to troubleshoot any more possible problems.



Brian

 

[btoscano]

I think I determined by process of elimination that the injection pump is the problem. After I reinstalled the fan belt and tried to crank it over... it wouldn't fire. I tried again, and no fire. Then I turned the engine over a few times with the barring tool... . OK. I started bleeding injectors to check for fuel. #1 empty, #2 lots, ... . I bled with the engine running rough and #2 pours fuel without any pressure. The engine would finally start running very roughly but #2 doesn't do much of anything except dump fuel.



I guess its time to pull the injectors and pump and have them all tested.



Brian

 

[btoscano]

Hey all,



The local diesel shop said the pump is in very bad shape and wants $1704 to rebuild it. They were not sure why it may have failed. They made varying suggestions that it could be anything from the fact that Cummins remans their pumps south of the border to the fuel I use. I asked them about the fact that the pump timing was off one tooth for a few weeks and they said that could be it too. Their suggestion was to get a core in better shape that they could rebuild.



Anybody have a good core they want to part with? I can travel within a few hundred miles of Nashville or Bristol if someone has one but doesn't want to ship it.



Brian